This invention relates to a steerable guidewire having an adjustable J-shaped distal tip that is adapted for use in small bore blood vessels such as the coronary arteries. Such guidewires typically are involved in percutaneous transluminal coronary angioplasty procedures. More particularly, the present invention concerns an improvement to the invention described in U.S. Pat. No. 4,719,924. That patent discloses a small diameter steerable guidewire having an adjustable flexible helical coil tip in which a pull wire extends the length of the guidewire, from its proximal to the distal tip of the coil. The distal tip of the guidewire normally assumes a generally straight configuration but can be altered to a J-shaped configuration upon tensioning of the pull wire. The degree of curvature of the distal tip is dependent on the extent to which the pull wire is tensioned.
Although the device described in U.S. Pat. No. 4,719,924 is highly effective in changing the curvature of the distal tip of the guidewire while the guidewire is in the patient's blood vessel, there are some instances in which it would be desirable for the distal tip of the guidewire to be more flexible so as to be able better to follow the contours and unanticipated tortuous configurations of the patient's blood vessel. When the pull wire is tensioned to cause the distal tip of the guidewire to assume a curved configuration, the tension on the pull wire tends to stiffen somewhat and retain the distal tip of the guidewire in that curved configuration and presents resistance to bending of the distal tip of the helical coil to a more straightened or altered curved configuration in order to follow the irregularities of the patient's blood vessel. Accordingly, there is a need for a small diameter steerable guidewire in which the curved configuration of the distal end of the guidewire can be adjusted from the proximal end of the guidewire while the guidewire is disposed within a patient's blood vessel yet which permits flexure of the curved distal end of the guidewire to a more straight or altered curved configuration in order to follow the contours of the patient's blood vessel. It is among the general objects of the invention to provide such a guidewire.